This bilingual technical article introduces variable frequency drives (VFDs), an industrial device for AC motor speed control. It details the VFD’s internal parts including the rectifier, DC bus, inverter and control circuit, as well as auxiliary cooling and protection components.

The paper explains the functions of main‑circuit and control terminals, together with standard wiring specifications, such as correct power‑and‑motor terminal connection, grounding requirements and anti‑interference cabling rules. It also provides frequently‑asked practical engineering questions.

Aimed at field engineers, this material offers practical guidance for VFD installation, commissioning and safe operation.